The invention relates to a method for processing signals, which are generated by the reflection of ultrasonic waves by defects in the surface of objects during the non-destructive testing of objects such as pipes, bars, sheet metal, or uniform and complex carbon-fiber components.
A method of the type mentioned at the outset is described in DE-A-10 2005 051 781, which relates to a method for the non-destructive inspection of a test piece using ultrasound. In the case of this method, ultrasound waves are coupled with one or a plurality of ultrasound transducers into the test piece and ultrasound waves reflected inside the test piece are received by a plurality of ultrasound transducers and converted into ultrasound signals. An ultrasound transducer is provided and activated on a surface of the test piece, such that the ultrasound waves coupled to the test piece are propagated spatially and distributed largely uniformly within the test piece. Subsequently, the ultrasound waves reflected within the test piece are received by a plurality m of ultrasound transducers provided on the surface and m ultrasound time signals are generated, in which time-resolved amplitude information is contained.
The m ultrasound time signals are saved. Subsequently, a 3-dimensional volume-image, a sector image in the form of a 2-dimensional ultrasound image through the test piece or an A-image in the form of a 1 dimensional time and location resolving ultrasound signal along a presettable intromission angle, is reconstructed exclusively using at least one part of the m ultrasound time signals.
DE-A-10 2006 003 978 relates to a method for the non-destructive inspection of a test piece having at least one acoustically anisotropic material area using ultrasound. The direction-specific sound propagation properties describing the acoustically anisotropic material area are determined and provided. Also a coupling of ultrasound waves takes place in the acoustically anisotropic material area of the test piece and a reception of ultrasound waves reflected in the interior of the test piece with a plurality of ultrasonic transducers.
The ultrasound signals generated by means of the plurality of ultrasonic transducers are evaluated such that the evaluation takes place in a direction-selective manner using the direction-specific sound propagation properties.
In the case of the method, a test piece is employed with n ultrasonic transducers, of which a number i ultrasonic transmitters is established, which are activated at the same time. Via the number i of the ultrasonic transmitters and the concrete assembly of the transmitter group, in particular its arrangement on the surface of the test piece, the entire radiation characteristic (aperture) of the transmitter group and in addition the sensitivity and the resolution power of the measurements is determined. Certainly, the number i is smaller than the total number of the ultrasound transmitters of the test piece. The total radiation characteristic is determined exclusively via the number i of the ultrasonic transmitters.
U.S. Pat. No. 4,989,143 relates to a coherent energy beam display and in particular to a new method for the improved adaptive formation of a coherent beam using interactive phase conjugating, in order to counteract effects of the inhomogeneous wave deflection. Details for the improvement of the signal energy and readout for phased array-applications for different defect depths cannot be learned from this publication.
A further method is described in EP-B-1 649 301. In the case of this method, a complete wavefront is emitted onto at least one test section of the object using a plurality of independent emission elements.
Subsequently, a wave reflected by the structure of the object is received by means of a plurality of receiver elements independent of one another. The signals received from the receiver elements are digitalized in digitalizing steps and processed further. A dynamic depth focusing or an aperture adaption is not raised in EP-B-1 649 301.
In U.S. Pat. No. 7,263,888 a two dimensional phased array for the volumetric ultrasound testing as well as a method for the use of the phased array is described. The phased array consists of a plurality of ultrasound oscillators, which are arranged in a right-angled design. The two-dimensional array permits the electronic adjustment of combustion point properties and of the dimensions of the aperture/orifice both in lateral as well as in height directions, so that uniform and/or specified sound-field characteristics can be attained at any or all positions in the tested components.
A modulation can be applied to each of the ultrasonic elements, in order to form a sample beam and to scan at least one area of the test material with the sample beam.
Compared to a 1-dimensional linear array, the 2-dimensional phased array offers the advantage that this is separated and/or divided in a plurality of discrete ultrasound oscillators, which extend both in the X as well as in the Z-direction. As a result, the formation of a sample beam can occur both in the X-Y plane as well as in the Z-Y plane. This permits a 3-dimensional steering/control of the sample beam with regard to the focal distance depth, steering angle and focal distance geometry. The steering of the aperture also contributes to the formation of the sample beam. The aperture of the array can be selected by multiplexing the sample beam by connecting synchronous channels with individual ultrasonic oscillators of the array. Also, the dimensions of the aperture can be controlled and/or adjusted both in the X as well as in the Z direction.
A method and a device for the ultrasonic testing of different zones of a workpiece are described in U.S. Pat. No. 5,533,401. A plurality of ultrasound transducers with focus zones with different sized depths is thereby arranged, in order to test a bar-shaped titanium-body with regard to its thickness. The focus zones partially overlap the adjacent focus zones, so that a complete inspection of the thickness of the entire bar section is ensured. The reflected signals of the transducer-receiver are processed in digital form, in order to generate an image of the bar-section.
Such a method, however, is expensive, since each probe must be adjusted individually and an adjustment of the surface unevenness is difficult.